Epitaxial growth of single crystal oxide thin films on silicon is of great interest in numerous device applications, e.g., ferroelectrics or high dielectric constant oxides for non-volatile high density memory and next generation MOS devices. Also, in the preparation of these films, it is pivotal to establish an ordered transition layer or buffer layer on the Si surface, especially for subsequent growth of single crystal oxides, e.g., perovskites.
Some reported growth of these oxides, such as BaO and BaTiO.sub.3 on Si (100) were based on a BaSi.sub.2 (cubic) template by depositing one fourth monolayer of Ba on Si (100) using molecular beam epitaxy at temperatures greater than 850.degree. C. See for example: R. McKee et al., Appl. Phys. Lett. 59(7), pp. 782-784 (Aug. 12 1991); R. McKee et al., Appl. Phys. Lett. 63(20), pp. 2818-2820 (Nov. 15 1993); R. McKee et al., Mat. Res. Soc. Symp. Proc., Vol. 21, pp. 131-135 (1991); U.S. Pat. No. 5,225,031, issued July 6, 1993, entitled "PROCESS FOR DEPOSITING AN OXIDE EPITAXIALLY ONTO A SILICON SUBSTRATE AND STRUCTURES PREPARED WITH THE PROCESS"; and U.S. Pat. No. 5,482,003, issued Jan. 9, 1996, entitled "PROCESS FOR DEPOSITING EPITAXIAL ALKALINE EARTH OXIDE ONTO A SUBSTRATE AND STRUCTURES PREPARED WITH THE PROCESS". A strontium silicide (SrSi.sub.2) interface model with a c(4.times.2) structure was proposed. See for example: R. McKee et al., Phys. Rev. Lett. 81(14), 3014 (Oct. 5 1998). However, atomic level simulation of this proposed structure indicates that it likely is not stable at elevated temperatures.
Growth of SrTiO.sub.3 on silicon (100) using an SrO buffer layer has been accomplished. See for example: T. Tambo et al., Jpn. J. Appl. Phys., Vol. 37 (1998), pp. 4454-4459. However, the SrO buffer layer was thick (100 .ANG.), thereby limiting application for transistor films, and crystallinity was not maintained throughout the growth.
Furthermore, SrTiO.sub.3 has been grown on silicon using thick oxide layers (60-120 .ANG.) of SrO or TiO. See for example: B. K. Moon et al., Jpn. J. Appl. Phys., Vol. 33 (1994), pp. 1472-1477. These thick buffer layers would limit the application for transistors.
In CMOS applications, these types of oxide layers are fabricated using molecular oxygen and are formed thin (less than 50 .ANG.). Accordingly, a result is leaky films in which high electrical leakage is experienced due to oxygen deficiencies or vacancies. Furthermore, these films require a post growth anneal in oxygen to reduce leakage current density across the oxide layer.
Therefore, a method for fabricating a high dielectric constant oxide on a semiconductor structure having low leakage current density is desired.
It is a purpose of the present invention to provide for a method of fabricating a high dielectric constant oxide on a semiconductor structure having low leakage current density.
It is a further purpose of the present invention to provide for a method of fabricating a high dielectric constant oxide on a semiconductor structure in which the gate dielectric leakage current density is near zero.
It is another purpose of the present invention to provide for a method of fabricating a high dielectric constant oxide on a semiconductor structure using activated or atomic oxygen, thus reducing leakage current density.